Pneumatic tire comprising a device for measuring a mechanical force and use of the device

ABSTRACT

The invention relates to a tire comprising an apparatus, wherein the apparatus comprises a first, second, third, fourth and fifth layer, the third layer being optional, characterized in that: a) the first layer comprises a first electrode material, b) the second layer comprises a first intermediate material, c) the third layer comprises an insulation material, d) the fourth layer comprises a second intermediate material, and e) the fifth layer comprises a second electrode material, wherein the second or fourth layer has a layer thickness in the range from 10 to 1000 μm, the first intermediate material of the second layer and the second intermediate material of the fourth layer are different, and the four or five layers are arranged one above the other according to the above sequence. The invention also relates to uses of the apparatus.

The invention relates to a tire comprising an apparatus, wherein the apparatus comprises a first, second, third, fourth and fifth layer, the third layer being optional. The invention also relates to uses of the apparatus.

Sensors are playing an ever greater role in today's automobile industry. They can not only help to monitor the material properties in the production or in the use of various automotive parts, but also make it possible to perceive effects of forces that would be perceptible only with difficulty, if at all, without them. It is often necessary here to mount the sensors at various points in the automobile in order to measure the changes in the material properties or acting forces directly in situ. The size of the sensors can also play a role here, and this should be at a minimum, in order that the mounting of the sensor does not entail any additional problems.

In addition, sensors can frequently be used only with the aid of a power source. The connection to the power source and the mounting of the power source at a suitable point additionally make it more difficult to install a sensor at an envisaged site.

One problem underlying the invention is that of providing an apparatus that enables measurement of mechanical forces in a tire during travel, for example lateral forces or braking forces. In particular, this should preferably be possible without the use of an additional electrical power source, and the apparatus should be particularly sensitive. In addition, another object of the invention was to provide an apparatus for charging an energy source in a tire or a wheel.

In general, this object is achieved according to the invention by an apparatus, characterized in that the apparatus comprises the following layers

-   -   a first layer comprising a first electrode material,     -   a further layer comprising a first intermediate material,     -   a further layer comprising a second intermediate material,         and     -   a further comprising a second electrode material,         wherein     -   the first intermediate material and the second intermediate         material are different. Preferably, the apparatus comprises         means for measuring the voltage between the first and fifth         layers comprising a second electrode material, or between the         layer comprising a first intermediate material and the layer         comprising a second intermediate material.

In the context of the present invention, the phrase “the four [ . . . ] layers are arranged one above the other according to the above sequence” means that the first layer is mounted directly on the second layer, the second layer directly on the fourth layer and the fourth layer directly on the fifth layer, with no further layers present between these four. This applies in particular to the four specific embodiments of the present invention described below.

In the context of the present invention, the term “fifth layer” is to be understood merely as a nomenclature of this layer and is not to be understood in such a way that there must be four additional layers present in addition to this fifth layer. The same applies to the second, third and fourth layers. Thus, for example, in an apparatus according to the invention, four layers can be present, wherein the four layers consist of a first, second, fourth and fifth layer. In this sense, within the context of the entire present invention, the first layer can also be designated as the top layer, the second layer as the upper middle layer, the third layer as the insulation layer, the fourth layer as the lower middle layer and the fifth layer as the bottom layer. This applies in particular to the four specific embodiments of the present invention described below.

All advantages of the above general solution of the object are described below by specific embodiments and apply mutatis mutandis to the above general embodiment.

In a first embodiment this object is achieved according to the invention by an apparatus for measuring a mechanical force, comprising a first, second, third, fourth and fifth layer, the third layer being optional, characterized in that

-   -   a) the first layer comprises a first electrode material,     -   b) the second layer comprises a first intermediate material,     -   c) the third layer comprises an insulation material,     -   d) the fourth layer comprises a second intermediate material,         and     -   e) the fifth layer comprises a second electrode material,         wherein     -   the second or fourth layer has a layer thickness in the range         from 10 to 1000 μm,     -   the first intermediate material of the second layer and the         second intermediate material of the fourth layer are different,         and     -   the four or five layers are arranged one above the other         according to the above sequence.

It has been found that, surprisingly, in the context of the present invention, in the event of friction between two different intermediate materials having the above-described dielectric conductivities in the second and fourth layers, sufficient electrons per unit area must be transferred for a sufficiently high voltage to arise on separation of these two intermediate materials rubbed against one another. The resultant voltage can then be exploited in order to generate an electrical signal. This electrical signal can be utilized in order to measure or even quantify the force that generates the original friction. In the context of the present invention, the second and fourth layers of an apparatus according to the invention comprise the respective intermediate materials which can be charged by contact and especially by friction. The presence of the first and second intermediate layers, i.e. the second and fourth layers of an apparatus according to the invention, causes higher voltages and current flows, and thus also higher powers to be achieved during current generation, or a more sensitive measuring apparatus during measurement, than with comparable apparatuses that are not according to the invention, in which only one intermediate layer is present between the two electrode materials.

Preference is given to an apparatus as described above, wherein the apparatus

-   -   is suitable for measuring a mechanical force         and/or     -   is suitable for generating an electrical voltage and for         electrically charging a battery and/or accumulator attached to a         wheel comprising the tire or attached to the tire, which is         preferably a tire in accordance with the invention described         below.

In addition, within the context of the present invention a third layer can be optionally present between the second and fourth layers, designed such that the second and fourth layers of an apparatus according to the invention can be separated from one another in a first state and come into contact with one another in a second state. The second state of an apparatus according to the invention may be triggered here by a force which acts at right angles to the layers and which causes contact between the second and fourth layers of an apparatus according to the invention. A crucial contribution made by the present invention is therefore that of having recognized that in the presence of the third layer between the second and fourth layers of an apparatus according to the invention as described above or as described above as preferred, more electrons can be transferred between the second and fourth layers in order to generate an electrical voltage between the second and fourth layers after separation of the contact between them. Subsequently, the electrons transferred in the second state can be kept separate by means of transition to a third state of the apparatus according to the invention. The transferred electrons lead to a difference in charge between the second and fourth layers and hence consequently also between the first and fifth layers of the apparatus according to the invention. The difference in voltage between the first and fifth layers is induced by the electrons transferred, while the fourth and second layers are removed from one another again after contact. The presence of a third layer can increase the voltage difference.

It has also been possible to show that by a suitable choice of the layer thickness of the second and/or fourth layer, in the following also called the transverse extent of the one layer, it was possible to further increase the voltage or electrical power generated in an apparatus according to the invention, and thus to achieve an even more sensitive measurement of forces on the apparatus according to the invention.

The voltage between the first and fifth layers of the apparatus according to the invention can be measured by means of a voltmeter. The apparatus according to the invention therefore preferably also has a voltmeter for measuring the voltage between the second and fourth layers or between the first and fifth layers of the apparatus according to the invention.

However, preference is given to an apparatus as described above or as described above as preferred, an apparatus for measuring a mechanical force, comprising a top layer, an upper middle layer, a lower middle layer and lower middle layer and no third layer, characterized in that

-   -   the top layer comprises a first electrode material,     -   the upper middle layer comprises a first intermediate material,     -   the lower middle layer comprises a second intermediate material,         and     -   the bottom layer comprises a second electrode material,         wherein     -   the first intermediate material of the upper middle layer and         the second intermediate material of the lower middle layer are         different,     -   the four layers are arranged one above the other according to         the above sequence,         and     -   the upper middle layer and/or the lower middle layer comprises         at least one filler in addition to the second intermediate         material.

Such an apparatus has in particular the advantages described below if it is fitted in a tire according to the invention as described below.

Preference is given to an apparatus as described above, characterized in that

for measuring a mechanical force, comprising a first, second, third, fourth and fifth layer, characterized in that

-   a) the first layer comprises a first electrode material, -   b) the second layer comprises a first intermediate material having a     dielectric conductivity e_(r) of greater than 1.01 F·m⁻¹, -   c) the third layer comprises an insulation material, -   d) the fourth layer comprises a second intermediate material having     a dielectric conductivity e_(r) of greater than 1.01 F·m⁻¹, -   and -   e) the fifth layer comprises a second electrode material, -   wherein     -   the first intermediate material of the second layer and the         second intermediate material of the fourth layer are different,     -   the five layers are arranged one above the other,     -   the second and fourth layers are separated from one another by         means of the third layer in a first state of the apparatus         and     -   the third layer is designed such that the second and fourth         layers can come into contact with one another in a second state         of the apparatus.

Preference is given to an apparatus as described above, characterized in that

-   -   a) the first layer consists of a first electrode material,     -   b) the second layer comprises a first intermediate material         having a dielectric conductivity e_(r) of greater than 1.01         F·m⁻¹,     -   c) the third layer comprises an insulation material,     -   d) the fourth layer comprises a second intermediate material         having a dielectric conductivity e_(r) of greater than 1.01         F·m⁻¹,         and     -   e) the fifth layer consists of a second electrode material,         wherein     -   the first intermediate material of the second layer and the         second intermediate material of the fourth layer are different,     -   the five layers are arranged one above the other,     -   the second and fourth layers are separated from one another by         means of the third layer in a first state of the apparatus         and     -   the third layer is designed such that the second and fourth         layers can come into contact with one another in a second state         of the apparatus.

Special preference is given to an apparatus as described above, characterized in that

-   a) the first layer consists of a first electrode material, -   b) the second layer consists of a first intermediate material having     a dielectric conductivity e_(r) of greater than 1.01 F·m⁻¹, -   c) the third layer comprises an insulation material, -   d) the fourth layer consists of a second intermediate material     having a dielectric conductivity e_(r) of greater than 1.01 F·m⁻¹, -   and -   e) the fifth layer consists of a second electrode material, -   wherein     -   the first intermediate material of the second layer and the         second intermediate material of the fourth layer are different,     -   the five layers are arranged one on top of another,     -   the second and fourth layers are separated from one another by         means of the third layer in a first state of the apparatus         and     -   the third layer is designed such that the second and fourth         layers can come into contact with one another in a second state         of the apparatus.

It is preferable in the context of the present invention that the transition of the apparatus from the first state to the second state is triggered by means of the action of a mechanical force on the apparatus according to the invention. It is more preferable, in addition, when the apparatus according to the invention in the second state is then converted to a third state as soon as the above-described mechanical force ceases to act on the apparatus according to the invention. The third state of the apparatus according to the invention differs from the first state of the apparatus according to the invention in that an electrical voltage can be measured between the second and fourth layers or between the first and fifth layers of the apparatus according to the invention.

In the context of the present invention, the expression “mechanical force” preferably encompasses any external action on an apparatus according to the invention that has the effect of converting the apparatus according to the invention from the first state to the second state. The above-described mechanical force should preferably act at right angles to the longitudinal extent of the five layers of the apparatus according to the invention.

Preference is given to an apparatus according to the invention as described above or as described above as preferred when the five layers lie one on top of another in the sequence specified above by the letters a), b), c), d) and e) and there are no further layers present between them.

It is more preferable when the apparatus according to the invention comprises a transmission unit which converts the voltage generated between the first and fifth layers of the apparatus according to the invention to an electromagnetic signal which can then be received by a receiving unit elsewhere in a space-saving manner. It is advantageous here when the signal contains information relating to the magnitude of the voltage, in order to be able to quantify the voltage and thus the mechanical force exerted.

In the context of the present invention, it is possible to use any material known in the prior art which is used in an electrode in the prior art for the first and second electrode materials of the apparatus according to the invention. Preferably, both electrode materials consist of the same material, especially the same metal. In the context of the present invention, preferred electrode materials are selected from the group consisting of: copper, aluminum, silver, iron oxide and carbon-based materials.

Particularly preferably, electrode materials are selected from the group consisting of: copper, aluminum, silver and carbon-based materials.

Particularly preferably, electrode materials are selected from the group consisting of: copper, aluminum, carbon fiber and rubber compounds with a specific conductivity at 20° C. of more than 1 S·cm⁻¹. Such rubber compounds are, in particular, rubber compounds with a carbon black content of more than 20 phr carbon black, particularly preferably more than 50 phr carbon black, very particularly preferably more than 80 phr carbon black.

In the context of the present invention, carbon-based materials are preferably graphite, graphene, carbon nanotubes, carbon black. The first and fifth layers do not have to have the same dimensions as the second and fourth layers and, in particular, can be smaller. It is also conceivable that the first and fifth layers are structured in a tissue-like manner and thus do not form continuous layers. It is also possible for the first and fifth layers to consist of one or more wires and/or fibers separated from one another. The function of the electrode material of the first and fifth layers of an apparatus according to the invention is primarily to guarantee the fast transport of electrons and can therefore be arbitrarily designed as long as this function is fulfilled.

In the context of the present invention, the first or second intermediate materials used may be any materials having a dielectric conductivity e_(r) of greater than 1.01 F·m⁻¹. In the context of the present invention, the intermediate material merely has the task of absorbing electrons from the respective other intermediate material and releasing them, and hence of generating a charge of correspondingly opposite polarity in the respective adjoining electrode material. The charge of opposite polarity generated in the electrode material generates a voltage between the first and fifth layers of the apparatus according to the invention. In the context of the present invention, it has been found that, surprisingly, intermediate materials having a dielectric conductivity e_(r) of greater than 1.01 F·m⁻¹ are sufficient to generate a sufficiently great voltage which can be utilized for measurement of the mechanical force.

It is additionally advantageous here when the insulation material of the third layer of an apparatus according to the invention preferably has a lower conductivity at 20° C. than the conductivity of the first intermediate material and the second intermediate material. A lower conductivity of the insulation material than the first and second intermediate materials would already be sufficient to at least briefly generate a voltage between the second and fourth layers or the first and fifth layers which can be utilized for generation of an electrical signal.

Particularly high mechanical forces can also generate particularly high voltages in the apparatus according to the invention, which can be utilized not just for measuring the mechanical force but also for charging a power storage means or for driving an electrically operated apparatus.

Preference is given to an apparatus as described above or as described above as preferred, the apparatus comprising a third layer and the second and fourth layers in a first state of the apparatus being separated by means of the third layer, the third layer being designed such that the second and fourth layers can come into contact with one another in a second state of the apparatus.

As described above, it is advantageous to have a third layer in an apparatus according to the invention, which ensures that the second and fourth layers are completely separated from one another, all the more so to achieve a maximum electrical power, i.e. the product of measured voltage to the current flow, of the apparatus according to the invention. However, it is also possible to achieve a current flow and thus a voltage between the second and fourth layers of the apparatus according to the invention, and thus also between the first and fifth layers, without the second and fourth layers completely separating from one another. In an apparatus according to the invention, a voltage and a current flow can also be generated if the fourth and second layers are permanently touching one another and only the force acting on them is varied. Such a preferred embodiment of the present invention is particularly advantageous for use in a vehicle tire, where a third layer as described above or below is difficult to implement. For the above reasons, a third layer is only optimal for an apparatus according to the invention.

Preference is given to an apparatus as described above or as described above as preferred, wherein the apparatus

-   -   additionally comprises means of measuring the voltage between         the first and fifth layers of the apparatus         and/or     -   comprises a transmitter unit suitable for generating an         electromagnetic signal from the voltage between the first and         fifth layers of the apparatus,         and/or     -   additionally enables means of contacting the first and second         electrode materials with the means of measuring the voltage or         with the transmitter unit.

It is preferable that the apparatus according to the invention comprises means of converting the electrical voltage generated to an RF signal, in which case the height of the voltage can also be read off from the RF signal. This means that the open-loop and/or closed-loop control unit that evaluates the signal need not be mounted in the same place as the apparatus according to the invention.

In the context of the present invention, the values of electrical conductivity, unless stated otherwise, are always based on values which have been measured under standard conditions, i.e. in particular at 20° C. and atmospheric pressure. Electrical conductivity can be carried out, for example, by standard ASTM E1004-17

Preference is given to an apparatus as described above or as described above as preferred, wherein the second and/or fourth layer comprises at least one filler in addition to the second intermediate material, the total amount of the at least one filler in the case of silica preferably being in a range from 0.1% by weight to 50% by weight, preferably in the range from 5% by weight to 25% by weight, particularly preferably in the range from 10% by weight to 20% by weight, very particularly preferably in the range from 13% by weight to 17% by weight, in each case as a proportion of the total mass of the second and/or fourth layer of the apparatus. Such an apparatus generates an even greater electrical power.

Preference is given to an apparatus as described above or as described above as preferred, wherein the total amount of the at least one filler in the second and/or fourth layer, in particular in the case of carbon black, is preferably in the range from 0.1% by weight to 50% by weight, preferably in the range from 1% by weight to 20% by weight, particularly preferably in the range from 1% by weight to 10% by weight, very particularly preferably in the range from 3% by weight to 7% by weight, in each case as a proportion of the total mass of the second and/or fourth layer of the apparatus.

Such an apparatus generates an even greater electrical power.

Preference is given to an apparatus as described above or as described above as preferred, wherein the third layer comprises an insulation material which at 20° C. has an electrical conductivity of less than 10⁻¹ S·cm⁻¹, preferably of less than 10⁻³ S·cm⁻¹, particularly preferably less than 10⁻⁶ S·cm⁻¹.

One advantage of the above-described aspect of the present invention is that

the above-described insulation materials, by virtue of their low electrical conductivity, keep the electrons that have been transferred in the second state of the apparatus according to the invention separate for a particularly long period.

Preference is given to an apparatus as described above or as described above as preferred, wherein each of the five layers has a transverse extent and two longitudinal faces, wherein

the total area of one longitudinal face of the second layer is in contact with the area of one longitudinal face of the first layer

and/or

the total area of one longitudinal face of the fourth layer is in contact with the area of one longitudinal face of the fifth layer.

One advantage of the above-described aspect of the present invention is that particularly area-covering contact between the layers enables faster induction of voltage between the first and fifth layers of the electrons between the respective layers.

In the context of the present invention, it is preferable when the transverse extent of a layer according to an apparatus of the invention runs parallel to the shortest extent of the layer and hence at right angles to the longitudinal faces of the layers of an apparatus according to the invention. It is particularly preferable when the longitudinal faces of the layers of an apparatus of the invention are the faces of the layers of the apparatus according to the invention that each adjoin the adjacent layer of the apparatus according to the invention. This applies both to all the above apparatuses according to the invention and to all of those described hereinafter.

Preference is given to an apparatus as described above or as described above as preferred, wherein each of the five layers has a transverse extent and two longitudinal faces, wherein, in the first state of the apparatus,

-   the total area of the first longitudinal face of the third layer is     in contact with the entire area of one longitudinal face of the     second layer -   and/or -   the total area of the second longitudinal face of the third layer is     in contact with the entire area of one longitudinal face of the     fourth layer -   and -   wherein in the second state of the apparatus according to the     invention,     -   at least 50% of the total surface area of the said longitudinal         face of the second layer, preferably at least 80%, are in         contact with the surface of the said longitudinal face of the         fourth layer         and     -   at least 50% of the total surface area of the said longitudinal         face of the fourth layer, preferably at least 80%, are in         contact with the surface of the said longitudinal face of the         second layer.

One advantage of the above-described aspect of the present invention is that, in the second state of the apparatus according to the invention, a particularly large number of electrons per unit longitudinal area can be transferred between the second and fourth layers.

Preference is given to an apparatus as described above or as described above as preferred, wherein

the first intermediate material of the second layer has a dielectric conductivity ε_(r) of greater than 1.1 F·m⁻¹, preferably greater than 1.5 F·m⁻¹, preferably greater than 2 F·m⁻¹, more preferably greater than 5 F·m⁻¹, most preferably greater than 10 F·m⁻¹,

and/or

the second intermediate material of the fourth layer has a dielectric conductivity e_(r) of greater than 1.1 F·m⁻¹, preferably greater than 1.5 F·m⁻¹, preferably greater than 2 F·m⁻¹, more preferably greater than 5 F·m⁻¹, most preferably greater than 10 F·m⁻¹.

One advantage of the above-described aspect of the present invention is that the above-described first and second intermediate materials can absorb a particularly large number of electrons and hence can generate particularly high voltage differences between the first and fifth layers of an apparatus according to the invention. This enables measurement of particularly small mechanical forces with an apparatus according to the invention.

More preferably, the dielectric conductivity e_(r) of one of the above-described first or second intermediate materials is not greater than 100 F·m⁻¹, most preferably not greater than 50 F·m⁻¹.

In the context of the present invention, the dielectric conductivity e_(r) of an intermediate material is also called relative permittivity e_(r) and is measured at 20° C. and a frequency of 50 Hz. The measurement can be carried out, for example, using a commercially available RLC measuring instrument according to a method known to the person skilled in the art.

The determination of the dielectric conductivity e_(r) is preferably carried out as follows using a commercially available RLC measuring instrument:

the loss factor Tan δ is indicated directly as the “DF: dissipation factor”,

while it must be calculated using the measurement results of the plate capacitor filled with dielectric material, or while it must preferably be calculated using the measurement results of an apparatus according to the invention.

When measuring the capacitance, it must be taken into account that, in addition to the capacitance of the electrodes that is sought, the capacitance of the supply line and the sample capacitor housing at the input of the bridge of the plate capacitor is also included. The resulting stray capacitance C_(F) is independent of the frequency and must be taken into account in the evaluation, i.e. subtracted.

Preference is given to an apparatus as described above or as described above as preferred, wherein the difference between the specific triboelectric affinity of the first intermediate material of the second layer and the specific triboelectric affinity of the second intermediate material of the fourth layer is at least 20 nC/J, preferably at least 40 nC/J, more preferably at least 60 nC/J, measured at 20° C. and at 35% relative air humidity.

One advantage of the above-described aspect of the present invention is that the first and second intermediate materials have not just sufficiently high permittivity as described above, but also have a sufficiently great difference in relation to the specific triboelectric affinity and hence can transfer a particularly large number of electrons on contact of the second layer with the fourth layer of the apparatus according to the invention in the second state.

In the context of the present invention, it has been found that those forces in the tire that act in the radial direction can be measured sufficiently well with a difference of 20 nC/J.

In the context of the present invention, it has likewise been found that those forces in the tire that act in the circumferential direction direction can be measured sufficiently well with a difference of 40 nC/J.

In the context of the present invention, it has likewise been found that lateral forces in the tire can be measured sufficiently well with a difference of 60 nC/J.

The measurement of the specific triboelectric affinity of an intermediate material, in the context of the above invention, was conducted at atmospheric pressure and 22° C. A sample consisting of an intermediate material with an area of 1 cm×1 cm, called intermediate material sample hereinafter, and a reference sample of acrylonitrile-butadiene rubber with an area of 1 cm×2 cm were provided. The reference sample was secured over its full area to a copper contact having an identical area of 1 cm×2 cm. The intermediate material sample and the reference sample were electrostatically neutralized with a “7006 AC GEN4 Ionizing Bar” from Exair. Subsequently, the intermediate material samples were superposed over the full area on one end of the reference sample with an area of 1 cm×2 cm. Subsequently, the sample materials were pressed together edge to edge with a force of 0.1 N over the superposed area of 1 cm² and, during the application of this force, the intermediate material sample was pulled from one end of the reference sample to the other end of the reference sample, such that it covered a distance of 1 cm. After adequate separation of the intermediate material sample and the reference sample and mounting of the intermediate material sample on an appropriate copper contact having an identical area of 1 cm×1 cm, the resultant voltage between the intermediate material sample and the reference was ascertained by means of an AlphaLab Surface DC Voltmeter SVM2 from “AlphaLab Inc.” The reciprocal of the voltage value thus obtained between the two contacts gives the above-described specific triboelectric affinity of the intermediate material examined.

The specific triboelectric affinity of the first and second intermediate materials should preferably not exceed 150 nC/J, and should more preferably not exceed 100 nC/J.

Preference is given to an apparatus as described above or as described above as preferred, wherein the third layer comprises a support border consisting of a vulcanized natural or synthetic rubber or a thermoset, and a mixture is present in the support border, the mixture comprising one or more gases and/or particles consisting of an insulation material, wherein the support border preferably has a thickness of 0 to 200 μm and/or a maximum electrical conductivity of 10 μS/m.

Preference is given to an apparatus as described above or as described above as preferred, wherein the third layer

-   consists of a mixture, wherein the mixture comprises a gas and     particles consisting of the insulation material or consists of a gas     and particles consisting of the insulation material, wherein the     insulation material is preferably selected from the group consisting     of wool, a resin, amber, wood, paper and polycarbonate.

Preferred gases are air, nitrogen or argon, but especially air. The particles may be in round form, in cord-like form or another form. They are preferably in cord-like form as in the case of wool with a longitudinal extent of 1 mm to 10 cm and a thickness of not more than 1 mm.

Preference is given to an apparatus as described above or as described above as preferred, wherein the third layer includes or consists of, as insulation material, a liquid having a viscosity at 20° C. in the range from 0.1 mPa·s to 10⁶ mPa·s, preferably having a viscosity at 20° C. in the range from 1 mPa·s to 10,000 mPa·s, more preferably having a viscosity at 20° C. in the range from 1 mPa·s to 100 mPa·s. More preferably, the third layer consists of the above-described liquid.

One advantage of the above-described aspect of the present invention is that liquids having the above-described viscosities and especially having the conductivities of the third layer that are described further up are of particularly good suitability as a third layer in an apparatus according to the invention. In this context, however, the third layer should be laterally delimited by a further material such that the above-described liquid remains in situ. This further material should be nonconductive with the conductivities described further up, since it would connect both the second and the fourth layer so as to impose boundaries on the above-described liquid.

Preference is given to an apparatus as described above or as described above as preferred, wherein the third layer comprises, as insulation material, a compound having a compression modulus in the range from 1 to 30 GPa, preferably having a compression modulus in the range from 5 to 10 GPa.

One advantage of the above-described aspect of the present invention is that compounds having the above-described compression moduli and especially having the conductivities of the third layer that are described further up are of particularly good suitability as a third layer in an apparatus according to the invention. In particular for use in a tire or industrial rubber articles such as conveyor belts, hoses and drive belts, but most particularly for tires.

Preference is given to an apparatus as described above or as described above as preferred, wherein the first intermediate material of the second layer comprises a solid material or consists primarily of a solid material selected from the group consisting of polyurethane, aluminum, polyamide, a mica, glass, polyacrylates, quartz, lead, silk, cellulose and mixtures thereof. The first intermediate material particularly preferably comprises or consists primarily of a solid material selected from the group consisting of polyurethane, polyamide, a mica, glass, polyacrylate, quartz, silk, poly(organo) siloxanes, cellulose and mixtures thereof.

Preference is also given to an apparatus as described above or as described above as especially preferred, wherein the first intermediate material of the second layer is nylon or aluminum. But glass and cellulose are also preferred, as they advantageously have a dielectric conductivity exceeding 2 F·m⁻¹.

Preference is given to an apparatus as described above or as described above as especially preferred, wherein the second intermediate material of the fourth layer comprises a solid material or consists primarily of a solid material selected from the group consisting of natural or synthetic rubber, polyester, polyethylene, polyethylene terephthalates, polypropylene, polystyrene, polychlorobutadiene, polyacrylonitrile, polyvinyl chloride, poly(organo) siloxanes, Teflon, polyimides, vulcanized rubber particles, fillers and mixtures thereof. Particularly preferably, the second intermediate material of the fourth layer comprises or consists primarily of a solid material selected from the group consisting of acetate silk, natural or synthetic rubber, epichlorohydrin rubber, polyester, polyethylene, polyethylene terephthalates, polypropylene, polystyrene, polychlorobutadiene, polyacrylonitrile, polyvinyl chloride, Teflon, polyimides, vulcanized rubber particles, fillers and their mixtures, wherein the natural or synthetic rubbers are preferably the rubbers BR, SBR, SSBR, PDMS, ISBR and epichlorohydrin rubber.

Within the scope of the present invention, the term “epichlorohydrin rubber” covers all polymers comprising epichlorohydrin as a monomer unit, in particular polymerized epichlorohydrin, block copolymer partly made from epichlorohydrin and terpolymers partly made from epichlorohydrin, in particular the terpolymer made from epichlorohydrin, epoxy ether (i.e. ethylene oxide) and allyl-glycidyl ether, under the name GECO.

Preference is also given to an apparatus as described above or as described above as especially preferred, wherein the second intermediate material of the fourth layer comprises natural or synthetic rubber, poly(organo) siloxanes, vulcanized rubber particles with surface-modified fluorohydrocarbon chains and mixtures thereof, wherein each of the second intermediate materials mentioned more preferably additionally comprises graphite, silica or carbon black. Particular preference is given to an apparatus as described above or as described above as especially preferred, wherein as second intermediate material of the fourth layer use is made of polyisoprene, poly(dimethyl) siloxanes, vulcanized rubber particles with surface-modified fluorohydrocarbon chains and mixtures thereof, wherein each of the second intermediate materials mentioned very especially preferably additionally comprises graphite. But preference is also given to natural or synthetic rubber, polyethylene, polypropylene, polyvinyl chloride or Teflon as a second intermediate material of the fourth layer, since they advantageously have a dielectric conductivity exceeding

2 F.·m^(·1), wherein the natural or synthetic rubbers are preferably the rubbers BR, SBR, SSBR, PDMS, ISBR and epichlorohydrin rubber.

Preference is given to an apparatus as described above or as described above as preferred, wherein the apparatus additionally comprises a stabilization shell for increasing the mechanical stability of the apparatus, which surrounds the entirety of the five layers.

One advantage of the above-described aspect of the present invention is that the stabilization shell keeps the layers in their places and imparts mechanical stability to the apparatus. It can also extend partly as far as between the fourth and second layers of an apparatus according to the invention, in order to help in the expansion of the third layer after the application of the mechanical force.

The stabilization shell may consist primarily or entirely of one of the following compounds: a resin, amber, wood, paper, polycarbonate, polyurethane, polyamide, polyacrylates, natural or synthetic rubber, polyester, polyethylene, polyethylene terephthalates, polypropylene, polystyrene, polychlorobutadiene, polyacrylonitrile, polyvinyl chloride, poly(organo) siloxanes, Teflon, polyimides, vulcanized rubber particles, fillers and mixtures thereof. Preferably, however, the stabilization shell consists of a resin, amber, wood, paper or polycarbonate.

Preference is given to an apparatus as described above or as described above as preferred, wherein

-   -   the second intermediate material of the fourth layer     -   comprises epichlorohydrin rubber or     -   consists primarily or entirely of epichlorohydrin rubber         and/or     -   the first intermediate material of the second layer     -   comprises poly(organo) siloxanes, preferably PDMS, or     -   consists primarily or entirely of poly(organo) siloxane,         preferably PDMS.

Such an apparatus according to the invention has a higher electrical power.

Preference is given to an apparatus as described above or as described above as preferred, wherein the surface of the second and/or fourth layer has a surface roughness R_(a) in the range from 0.1 μm to 500 μm, preferably in the range from 0.5 to 100 μm, particularly preferably in the range from 1 to 50 μm, very particularly preferably in the range from 1 to 5 μm, measured according to DIN EN ISO 4288:1998. The said surface of the second and/or fourth layer in the context of the present invention is always the surface of the second and/or fourth layer facing the third layer. Such an apparatus according to the invention has a higher electrical power.

Preference is given to an apparatus as described above or as described above as preferred, wherein the second and/or fourth layer have a layer thickness in the range in the range from 10 to 1000 μm, preferably in the range from 30 to 300 μm, particularly preferably in the range from 70 to 160 μm or from 101 to 160 μm, very particularly preferably in the range from 110 to 130 μm.

Such an apparatus according to the invention has a higher electrical power.

Preference is given to an apparatus as described above or as described above as preferred, wherein each of the five layers has a longitudinal extent at right angles to the transverse extent and

-   the longitudinal extent of every single one of the five layers is in     the range from 0.1 to 1000 mm, preferably in the range from 0.1 to     100 mm, more preferably in the range from 0.1 to 10 mm,     and/or -   the transverse extent of every single one of the five layers is in     the range from 0.01 to 10 mm, preferably in the range from 0.01 to 1     mm, more preferably in the range from 0.01 to 0.1 mm.

One advantage of the above-described aspect of the present invention is that the above dimensions are of particularly good suitability for measuring a mechanical force in tires or industrial rubber articles such as conveyor belts, hoses and drive belts, but most particularly for tires.

A particularly high degree of preference is given to an apparatus as described above, characterized in that

-   a) the first layer consists of a first electrode material, -   b) the second layer consists of a first intermediate material, -   c) the third layer comprises an insulation material, -   d) the fourth layer consists of a second intermediate material, -   and -   e) the fifth layer consists of a second electrode material, -   wherein -   the first intermediate material of the second layer and the second     intermediate material of the fourth layer are different, -   the five layers are arranged one above the other, -   the second and fourth layers are separated from one another by means     of the third layer in a first state of the apparatus, -   the third layer is designed such that the second and fourth layers     can come into contact with one another in a second state of the     apparatus, -   the insulation material of the third layer at 20° C. has an     electrical conductivity of less than 10⁻³ S·cm⁻¹, -   each of the five layers has a transverse extent and two longitudinal     faces, wherein the entire area of one longitudinal face of the     second layer is in contact with the area of one longitudinal face of     the first layer and the entire area of one longitudinal face of the     fourth layer is in contact with the area of one longitudinal face of     the fifth layer, -   in the first state of the apparatus, the entire area of the first     longitudinal face of the third layer is in contact with the area of     one longitudinal face of the second layer and the entire area of the     second longitudinal face of the third layer is in contact with the     area of one longitudinal face of the fourth layer, -   the third layer, as insulation material, a liquid having a viscosity     at 20° C. in the range from 1 mPa·s to 100 mPa·s, -   the first intermediate material of the second layer consists of     nylon or aluminum, -   the second intermediate material of the fourth layer consists of a     mixture of solid polydimethylsiloxane and solid particles of     graphite -   and -   each of the five layers has a longitudinal extent at right angles to     the transverse extent and the longitudinal extent of every single     one of the five layers is in the range from 0.1 to 100 mm and the     transverse extent of every single one of the five layers is in the     range from 0.01 to 1 mm.

The above-described advantageous aspects of an apparatus according to the invention for measuring a mechanical force are also applicable to all aspects of a tire or industrial rubber article described hereinafter, and the advantageous aspects of tires or industrial rubber articles according to the invention that are discussed hereinafter are correspondingly applicable to all aspects of an apparatus according to the invention for measuring a mechanical force.

The invention also relates to a tire or an industrial rubber article comprising an apparatus according to any of the preceding claims and optionally, means of measuring the voltage between the first and fifth layers of the apparatus or between the second and fourth layers of the apparatus.

Industrial rubber articles are preferably conveyor belts, hoses and drive belts.

Preferably, a tire according to the invention is a pneumatic tire, more preferably a pneumatic vehicle tire, most preferably a pneumatic vehicle tire for utility vehicles or cars, very especially preferably a pneumatic vehicle tire for cars.

Preference is given to a tire as described above or as described above as preferred, wherein

-   the apparatus is mounted in the tread of the tire -   and

the central axis of the apparatus runs in the axial direction or in the circumferential direction of the tire.

One advantage of the above-described aspect of the present invention is that braking or acceleration forces in circumferential direction and lateral forces in axial direction can be measured while driving.

In the context of the present invention, the central axis of an apparatus according to the invention preferably runs through the geometric center of the third layer of the apparatus according to the invention and at right angles to the longitudinal extent of the third layer, wherein the longitudinal extent of the third layer is preferably exactly at the midpoint between the two longitudinal faces of the third layer of the apparatus according to the invention.

Preference is given to a tire as described above or as described above as preferred, comprising an apparatus, wherein the apparatus comprises a first, second, third, fourth and fifth layer, the third layer being optional,

characterized in that

-   -   a) the first layer comprises a first electrode material,     -   b) the second layer comprises a first intermediate material,     -   c) the third layer comprises an insulation material,     -   d) the fourth layer comprises a second intermediate material,         and     -   e) the fifth layer comprises a second electrode material,         wherein     -   the second or fourth layer has a layer thickness in the range         from 10 to 1000 μm,     -   the first intermediate material of the second layer and the         second intermediate material of the fourth layer are different,     -   the four or five layers are arranged one above the other         according to the above sequence.

Preference is given to a tire as described above or as described above as preferred, wherein the apparatus

-   -   comprises means for measuring the voltage between the first and         fifth layers or the second and fourth layers of the apparatus         and/or     -   is suitable for generating an electrical voltage and for         electrically charging a battery and/or accumulator attached to a         wheel comprising the tire or attached to the tire.

Preference is given to a tire as described above or as described above as preferred, wherein the second and/or fourth layer have a layer thickness in the range from 10 to 1000 μm, preferably in the range from 30 to 300 μm, particularly preferably in the range from 70 to 160 μm or from 101 to 160 μm, very particularly preferably in the range from 110 to 130 μm.

Preference is given to a tire as described above or as described above as preferred, with the second and/or fourth layer comprising at least one filler in addition to the second intermediate material.

Preference is given to a tire as described above or as described above as preferred, wherein the at least one filler

-   -   of the second layer is carbon black and/or silica,         and/or     -   of the fourth layer is carbon black and/or silica.

Preference is given to a tire as described above or as described above as preferred, wherein the at least one filler

-   -   in the second layer and/or     -   in the fourth layer or

is in an amount in the range from 0.1% by weight to 50% by weight, preferably in the range from 1% by weight to 20% by weight, particularly preferably in the range from 1% by weight to 10% by weight, very particularly preferably in the range from 3% by weight to 7% by weight, in each case as a proportion of the total mass of the first and/or fifth layer of the apparatus.

Preference is given to a tire as described above or as described above as preferred, wherein

-   -   the first intermediate material of the second layer has a         dielectric conductivity E_(r) of greater than 1.01 F·m⁻¹,         preferably of greater than 1.1 F·m⁻¹.         and/or     -   the second intermediate material of the fourth layer has a         dielectric conductivity e_(r) of greater than 1.01 F·m⁻¹,         preferably of greater than 1.1 F·m⁻¹.

Preference is given to a tire as described above or as described above as preferred, wherein the difference between the specific triboelectric affinity of the first intermediate material of the second layer and the specific triboelectric affinity of the second intermediate material of the fourth layer is at least 20 nC/J, measured at 20° C. and at 35% relative air humidity.

Preference is given to a tire as described above or as described above as preferred, wherein

-   -   the first intermediate material of the second layer comprises a         solid material or consists primarily of a solid material         selected from the group consisting of polyurethane, a mica,         glass, quartz, silk, poly(organo) siloxanes, cellulose and         mixtures thereof, and/or     -   the second intermediate material of the fourth layer comprises a         solid material or consists primarily of a solid material         selected from the group consisting of acetate silk, natural or         synthetic rubber, polyester, polyethylene, polyethylene         terephthalates, polypropylene, polystyrene, polychlorobutadiene,         polyacrylonitrile, polyvinyl chloride, poly(organo) siloxanes,         vulcanized rubber particles, fillers and their mixtures, wherein         the natural or synthetic rubbers are preferably the rubbers NR,         ENR, BR, SBR, SSBR, PDMS, ESBR and epichlorohydrin rubber.

Preference is given to a tire as described above or as described above as preferred, wherein

-   -   the first intermediate material of the second layer comprises a         solid material or consists primarily of a solid material         selected from the group consisting of polyurethane, a mica,         glass, quartz, silk, poly(organo) siloxanes, cellulose and         mixtures thereof, and/or     -   the second intermediate material of the fourth layer comprises a         solid material or consists primarily of a solid material         selected from the group consisting of acetate silk, natural or         synthetic rubber, polychlorobutadiene, polyacrylonitrile,         polyvinyl chloride, vulcanized rubber particles, fillers and         their mixtures and also optionally poly(organo) siloxanes,         wherein the natural or synthetic rubbers are preferably the         rubbers NR, ENR, BR, SBR, SSBR, PDMS, ESBR and epichlorohydrin         rubber.

Preference is given to a tire as described above or as described above as preferred, wherein

-   -   the first intermediate material of the second layer comprises a         solid material or consists primarily of a solid material         selected from the group consisting of polyurethane, poly(organo)         siloxanes, cellulose and mixtures thereof, and/or     -   the second intermediate material of the fourth layer comprises a         solid material or consists primarily of a solid material         selected from the group consisting of natural rubber, polyester,         epichlorohydrin rubber, polyethylene terephthalates,         polystyrene, polychlorobutadiene, polyacrylonitrile, polyvinyl         chloride and mixtures thereof, and optionally additionally         poly(organo) siloxanes.

Preference is given to a tire as described above or as described above as preferred, wherein the second intermediate material of the fourth layer

-   -   comprises epichlorohydrin rubber or     -   consists primarily or entirely of epichlorohydrin rubber         and/or

the first intermediate material of the second layer

-   -   comprises poly(organo) siloxanes, preferably PDMS, or     -   consists primarily or entirely of poly(organo) siloxane,         preferably PDMS.

Preference is given to a tire as described above or as described above as preferred, wherein the apparatus comprises a third layer between the second and fourth layer and the third layer comprises an insulation material.

Preference is given to a tire as described above or as described above as being preferred, wherein the third layer has an insulation material which at 20° C. has a specific electrical conductivity of less than 10⁻¹ S·cm⁻¹.

Preference is given to a tire as described above or as described above as preferred, wherein the third layer

-   -   comprises a support border consisting of a vulcanized rubber or         a thermoset and a mixture is present in the support border, the         mixture comprising one or more gases and/or particles consisting         of an insulation material, wherein the support border preferably         has a thickness of 0 to 200 μm and/or a maximum electrical         conductivity of 10 μS/m, or     -   the insulation material is a fluid with a viscosity in the range         from 0.1 mPa·s to 10⁶ mPa·s at 20° C., the viscosity being         measured by means of a rotational viscometer in accordance with         DIN EN ISO 3219.

Preference is given to a tire as described above or as described above as preferred, wherein

-   -   the apparatus is mounted in the tread of the tire and/or     -   the central axis of the apparatus extends in the radial         direction, in the axial direction or in the circumferential         direction of the tire, preferably in the axial direction or in         the circumferential direction of the tire, particularly         preferably in the circumferential direction of the tire.

The above-described advantageous aspects of an apparatus according to the invention for measuring a mechanical force or of a tire or industrial rubber article according to the invention are also applicable to all aspects of one of the uses of an apparatus that are described hereinafter, and the advantageous aspects of one of the uses according to the invention of an apparatus that are discussed hereinafter are correspondingly applicable to all aspects of an apparatus according to the invention for measuring a mechanical force or of a tire or industrial rubber article according to the invention.

The invention also relates to a use of an apparatus as described above or as described above as preferred for measuring a mechanical force along the transverse extent of the third layer of the apparatus according to the invention or along the midpoint axis of the apparatus according to the invention.

The invention also relates to a use of an apparatus as described above or as described above as preferred

-   -   to generate an electrical voltage, preferably in the tire,         and/or     -   to measure a mechanical force along the circumferential         direction or the axial direction in a tire.

The invention also relates to a use of an apparatus as described above or as described above as preferred for generating an electrical voltage between the first and fifth layers of the apparatus or between the second and fourth layers of the apparatus, the voltage preferably being used to charge an energy storage device, such as a battery or another accumulator on the wheel or tire. Thus, the force acting on the apparatus according to the invention is converted into charge stored in the energy storage device.

Other advantageous aspects of the present invention are listed in the following as aspects, with the numbers in brackets referring to the reference signs in the attached figures:

1. Apparatus for measuring a mechanical force (12), comprising a first, second, third, fourth and fifth layer (1, 2, 3, 4, 5),

characterized in that

-   -   a) the first layer (1) comprises a first electrode material,     -   b) the second layer (2) comprises a first intermediate material         having a dielectric conductivity e_(r) of greater than 1.01         F·m⁻¹,     -   c) the third layer (3) comprises an insulation material (9),     -   d) the fourth layer (4) comprises a second intermediate material         having a dielectric conductivity e_(r) of greater than 1.01         F·m⁻¹,         and     -   e) the fifth layer (5) comprises a second electrode material,         wherein     -   the first intermediate material of the second layer (2) and the         second intermediate material of the fourth layer (4) are         different,     -   the five layers are arranged one above the other,     -   the second and fourth layers (2, 4) are separated from one         another by means of the third layer (3) in a first state of the         apparatus (6)         and     -   the third layer (3) is designed such that the second and fourth         layers (2, 4) can come into contact with one another in a second         state of the apparatus (6).

2. Apparatus according to aspect 1, wherein

-   the insulation material (9) of the third layer (3) at 20° C. has an     electrical conductivity of less than 10⁻¹ S·cm⁻¹.

3. The apparatus according to any of the preceding aspects, wherein

-   the first intermediate material of the second layer (2) has a     dielectric conductivity E_(r) of greater than 1.1 F·m⁻¹ -   and/or -   the second intermediate material of the fourth layer (4) has a     dielectric conductivity e_(r) of greater than 1.1 F·m⁻¹.

4. Apparatus according to any of the preceding aspects, wherein the difference between the specific triboelectric affinity of the first intermediate material of the second layer (2) and the specific triboelectric affinity of the second intermediate material of the fourth layer (4) is at least 20 nC/J, measured at 20° C. and at 35% relative air humidity.

5. Apparatus according to any of the preceding aspects, wherein the third layer (3)

-   -   consists of a mixture, wherein the mixture comprises a gas and         particles consisting of the insulation material (9),         or     -   as insulation material (9) includes a liquid having a viscosity         at 20° C. in the range from 0.1 mPa·s to 10⁶ mPa·s.

6. The apparatus according to any of the preceding aspects, wherein

-   -   the first intermediate material of the second layer (2)         comprises a solid material or consists primarily of a solid         material selected from the group consisting of polyurethane,         aluminum, polyamide, a mica, glass, polyacrylates, quartz, lead,         silk, cellulose and mixtures thereof,         and/or     -   the second intermediate material of the fourth layer (4)         comprises a solid material or consists primarily of a solid         material selected from the group consisting of acetate silk,         natural or synthetic rubber, polyester, polyethylene,         polyethylene terephthalates, polypropylene, polystyrene,         polychlorobutadiene, polyacrylonitrile, polyvinyl chloride,         poly(organo) siloxane, Teflon, polyimides, vulcanized rubber         particles, fillers and their mixtures, wherein the natural or         synthetic rubbers are preferably the rubbers BR, SBR, SSBR,         PDMS, ISBR and epichlorohydrin rubber.

7. Apparatus according to any of the preceding aspects, wherein apparatus (6) additionally comprises a stabilization shell (7) for increasing the mechanical stability of the apparatus (6) which encloses the entirety of the five layers (1, 2, 3, 4, 5).

8. A tire (24) or industrial rubber article comprising an apparatus (6) according to any of the preceding aspects and means (13) of measuring the voltage between the first and fifth layers (1, 5) of the apparatus (6).

9. Tire according to aspect 8, wherein

-   the apparatus (6) is mounted in the tread (25) of the tire (24) -   and -   the central axis (19) of the apparatus (6) runs in the axial     direction (14) or in the circumferential direction (15) of the tire     (6.

10. Use of an apparatus according to any of the aspects 1 to 7 for measuring a mechanical force (12) along the transverse extent (18) of the third layer (3) of the apparatus (6).

11. Use of an apparatus according to any of the aspects 1 to 7 for generating an electrical voltage between the first and fifth layers (1, 5) of the apparatus (6).

DESCRIPTION OF FIGURES

FIG. 1 Cross section through a schematic apparatus according to the invention in a first state before application of a mechanical force, with the plane of intersection of the cross section running parallel to the central axis of the apparatus;

FIG. 2 Cross section through a schematic apparatus according to the invention in a second state during application of a mechanical force, with the plane of intersection of the cross section running parallel to the central axis of the apparatus;

FIG. 3 Cross section through a schematic apparatus according to the invention in a third state after application of a mechanical force, with the plane of intersection of the cross section running parallel to the central axis of the apparatus;

FIG. 4 Cross section through a schematic tire according to the invention, with the plane of intersection of the cross section running at right angles to the axial direction of the tire;

FIG. 5 a schematic representation of a measuring device for determining the electrical power of an apparatus according to the invention.

FIG. 1 shows a schematic diagram of an apparatus 6 according to the invention, comprising five layers 1, 2, 3, 4, 5, a voltmeter 13 and a stabilization shell 7 in one embodiment. FIG. 1 shows a cross-sectional view of the apparatus 6 according to the invention, with the plane of intersection of the cross section running parallel to the central axis 19 of the apparatus 6. The central axis 19 of the apparatus 6 runs parallel to the transverse extent 18 of the various layers and through the geometric center 23 of the third layer 3 of an apparatus 6 according to the invention, and at right angles to the longitudinal extent 17 of the various layers (only the longitudinal extent 17 of the first layer 1 is shown in FIG. 1 ). FIG. 1 also shows the longitudinal faces 20 of the fourth layer 4 and the longitudinal faces 21 of the fifth layer 5 in schematic form in cross section. In addition, FIG. 1 shows, in schematic form, that the third layer 3, as described above, comprises a compressible compound 9 having a compression modulus and as an example of an insulation material. The apparatus 6 shown in FIG. 1 is in a first state, with no external mechanical force acting on the apparatus 6 according to the invention. In this first state, the third layer 3 separates the second layer 2 from the fourth layer 4. Since there is no contact between the second layer 2 and the fourth layer 4 in the first state of the apparatus 6 according to the invention, no electrons can be transferred between the second layer 2 and the fourth layer 4.

FIG. 2 shows a schematic diagram of an apparatus 6 according to the invention, comprising five layers 1, 2, 3, 4, 5, a voltmeter 13 and a stabilization shell 7 in a further embodiment. FIG. 2 shows a cross-sectional view of the apparatus 6 according to the invention, with the plane of intersection of the cross section running parallel to the central axis 19 of the apparatus 6. The central axis 19 of the apparatus 6 runs parallel to the transverse extent of the five layers 1, 2, 3, 4, 5 and at right angles to the longitudinal extent 17 of the five layers 1, 2, 3, 4, 5, and through the geometric center 23 of the third layer 3 of an apparatus 6 according to the invention. FIG. 2 shows, in schematic form, that the third layer 3 is compressed, since a mechanical force 12 is acting on the apparatus 6 according to the invention. The apparatus 6 shown in FIG. 2 is therefore in the second state, which follows on from the first state in the time sequence, with the mechanical force 12 acting on the apparatus 6 according to the invention from above and below in the example shown in FIG. 2 . In this second state, the second layer 2 and the fourth layer 4 are in contact with one another. The contact between the second layer 2 and the fourth layer 4 in the second state of the apparatus 6 according to the invention enables transfer of electrons 11 from the second layer 2 to the fourth layer 4, and hence enrichment of the fourth layer 4 with additional negative charges 11 in the form of transferred electrons. This does not yet enable the development of an electrical voltage between the first and fifth layers, and this only occurs on removal of the second layer 2 and the fourth layer 4 from one another.

FIG. 3 shows a schematic diagram of an apparatus 6 according to the invention, comprising five layers 1, 2, 3, 4, 5, a voltmeter 13 and a stabilization shell 7 in a further embodiment. FIG. 3 shows a cross-sectional view of the apparatus 6 according to the invention, with the plane of intersection of the cross section running parallel to the central axis 23 of the apparatus 6. The central axis 23 of the apparatus 6 runs parallel to the transverse extent of the five layers 1, 2, 3, 4, 5 and at right angles to the longitudinal extent of the five layers 1, 2, 3, 4, 5, and through the geometric center 23 of the third layer 3 of an apparatus 6 according to the invention. FIG. 3 also shows, in schematic form, the longitudinal faces 22 of the third layer 3. In addition, FIG. 3 shows, in schematic form, in cross section, that the third layer 3 comprises a compressible compound 9 having a compression modulus as described above. The apparatus 6 shown in FIG. 3 is in a third state which differs from the first state of an apparatus 6 according to the invention merely in that the distribution of the electrons between the first, second, fourth and fifth layers 1, 2, 4, 5 is different compared to the first state.

In this third state, the third layer 3 separates the second layer 2 from the fourth layer 4, with the second layer 2 comprising fewer electrons, i.e. lacking negative charges 10, compared to the first state of the apparatus 6 according to the invention. The fourth layer 4 then additionally comprises the transferred electrons 11 compared to the first state of the apparatus 6 according to the invention. In order to compensate for this electrical charge differential, electrons can then flow from the fifth layer 5 into the first layer 1. The further the second layer 2 and the fourth layer 4 are removed from one another, the higher the voltage between the fifth layer 5 and the first layer 1. The distribution of charge between the fourth layer 4 and the second layer 2 remains the same in terms of magnitude.

This flow of the electrons is reversed as soon as the fourth layer 4 and the second layer 2 approach one another again until they touch, i.e. go back into the second state as shown in FIG. 2 . The apparatus 6 according to the invention can thus then be converted from the second to the third state or from the third to the second state as often as desired by applying a mechanical force, and hence the electrons, as described above, can be shifted in an ever-alternating manner from the fifth layer 5 into the first layer 1 and vice versa.

FIG. 4 shows a schematic diagram of a tire 24 according to the invention, comprising three apparatuses 6 according to the invention for measuring a mechanical force in a further embodiment in cross-sectional view, with the plane of intersection of the cross section running at right angles to the axis of rotation 14 of the tire 24. The three apparatuses 6 according to the invention are arranged in the tread 25 or on the inner liner 28 of the tire 24 according to the invention, with the central axis 19 of one apparatus 6 according to the invention running parallel to the circumferential direction 15 or parallel to the radial direction 16 of the tire 24 according to the invention. According to the direction in which the central axis 19 of an apparatus 6 according to the invention runs in the tread 25 of a tire 24 according to the invention, it is possible in a particularly efficient manner to measure those mechanical forces that run parallel to the central axis 19 of the apparatus 6 according to the invention. Thus, if the central axis 19 of the apparatus 6 according to the invention runs parallel to the circumferential direction 15, it is possible in an especially efficient manner to measure the braking and acceleration forces while driving with a tire 6 according to the invention. If the central axis 19 of the apparatus 6 according to the invention runs parallel to the axis of rotation 14, it is possible in an especially efficient manner to measure the lateral forces that arrive when cornering with a tire 6 according to the invention. If the central axis 19 of an apparatus 6 according to the invention runs parallel to the radial direction 16 of the tire 6 according to the invention in the tread 25, there are particularly strong mechanical forces acting on the apparatus 6 according to the invention whenever the apparatus 6 according to the invention is in the part of the tread 25 that constitutes what is called the footprint of the tire 6 according to the invention.

FIG. 5 shows a schematic representation of a measuring device 29 for determining the performance of an apparatus 1 according to the invention in a further embodiment, wherein the measuring device comprises an apparatus according to the invention 1, a flywheel 30 with a piston 31, and a stabilization shell 7 with a polycarbonate stamp 34 and a polycarbonate base 35. The stabilization shell 7 also comprises a polycarbonate border 38 with holes. The holes in the border 38 are used to allow a smooth escape and filling of the interior of the border 38 with air during the rotation of the flywheel 30. The rotation of the flywheel 30 causes the upper part 32 of the measuring device 29 to be moved up and down with the stamp 34 and the first and second layers 1, 2. Unless otherwise stated, the rotation took place at a frequency of 5 Hz, i.e. 5 revolutions per second. An oscilloscope 39 connected to the first and second electrode layer 1, 5, i.e. to the first and fifth layers 1, 5 of the apparatus 6 according to the invention, was used to determine the no-load voltage between the first and second electrode layer 1, 5 via the formula V₀=V_(L)/(R_(S)+R_(L)) and the associated no-load current. The circuit of the oscilloscope 39 is shown schematically in FIG. 5 with the voltage source V_(L) and the resistors R_(S) and R_(L), wherein the contacts to the indicated electrical circuit are connected to the first layer 1 and to the fifth layer 5 of the apparatus 1 according to the invention.

EXPERIMENTAL EXAMPLES

Test Methods

1. Surface roughness R_(a)

The results were ascertained in accordance with the

DIN EN ISO 4288:1998 method.

2. Electrical measurement in open-circuit conditions

The values for the open-circuit voltage and the no-load current were measured using the oscilloscope “Rigol Oscilloscope DS 4014” using the measuring device shown in FIG. 5 with a rotation frequency of the flywheel of 5 Hz. The diameter of the flywheel was 4 cm and the maximum distance between the second and fourth layers during rotation was 2.5 cm and the minimum distance was 0 cm. The oscilloscope had the following settings:

-   -   Attenuation ratio: 10:1     -   Input resistance: 10 MΩ±2%     -   Input capacitance: 13 pF±3 pF     -   Maximum input CAT II 300 VAC     -   Compensation range: 6 pF-24 pF.

By the rotation of the flywheel, the second and fourth layers were periodically pressed against one another and removed from one another again. Thus, measurable voltages between the electrodes, i.e. between the first and fifth layers, are measured and from these corresponding current flows for the no-load or open circuit condition are determined, also called no-load current flows. These measurable no-load voltages and the resulting no-load current strengths were recorded by the oscilloscope in the form of periodic peaks, the period of the peaks corresponding to the frequency of rotation of the flywheel. The values recorded in Tables 2 to 4 for the open-circuit voltage and the open-circuit current level correspond in each case to the value of the difference between the maximum and the minimum of the measured peaks. Corresponding tests in which an apparatus according to the invention was used without a third layer as described above, i.e. in which the second and fourth layers were continuously touching one another and only the force acting on the second and fourth layers was changed, produced the same trends as the test results shown below.

Production:

TABLE 1 Compositions of the second and fourth layers used in the apparatus according to the invention: 2nd 3rd 4th material quantity layer layer layer GECO phr — — 100  PDMS phr 100 — — Filler phr — — see Table 2 ZnO phr — — 3 Stearic acid phr — — 2 TMTD phr — —   2.5 MBTS phr — — 1 Dicumyl phr    0.2 — — Peroxide Sulfur phr — — 1 Air % by — 100 — wt. *GECO = terpolymer of epichlorohydrin, ethylene oxide and allyl-glycidyl ether; ** PDMS = polydimethylsiloxane

The second layer of PDMS and the fourth layer of GECO are produced according to a standard prior-art production process, which included the steps of mixing, rolling and vulcanizing the respective rubber mixture according to Table 1 for the second and fourth layers. The mixing of the respective rubber mixture was carried out after adding the components into a Banbury mixer at 70° C. with a rotor speed of 60 rpm for 8 minutes. The rolling was carried out with a two-roll mill for 10 minutes, so that a layer thickness of 120 μm was obtained in the finished vulcanized layer (with the exception of the fourth layer in the E7 and E8 experiments in Table 4). The vulcanization was performed in a rectangular vulcanizing mold at the standard temperatures of 120° C. for 10 minutes. The layers produced in this way had a length of 100 mm and a height of 30 mm.

For the roughened surfaces of the fourth layers of examples E5 and E6, a mold segment of the vulcanizing mold which was roughened by sandblasting was used in their vulcanization. The sandblasting on the corresponding mold segment is carried out in such a way that surface roughnesses R_(a) of 5 μm according to method DIN EN ISO 4288:1998 were achieved on the side facing the third layer.

Measurement Results:

Filler Content:

TABLE 2 Experimental data for the apparatus according to the invention with varying filler components: Exp. Exp. Exp. Exp. Exp. Property Units V0 E1 E2 E3 E4 Materials used in the layers of an apparatus according to the invention 1st layer Copper Copper Copper Copper Copper 2nd layer PDMS PDMS PDMS PDMS PDMS 3rd layer Air Air Air Air Air 4th layer GECO GECO GECO GECO GECO 5th layer Copper Copper Copper Copper Copper Thickness/ μm 120 120 120  120 120  transverse extent of the 2nd and 4th layer Filler type in — Silica¹ Silica¹ Carbon Carbon the 4th layer black² black² (GECO) Filler weight in phr  0  10 40  5 15 the 4th layer as a percentage of the total weight of the fourth layer Results No-load voltage V 125 185 63 153 97 measured from peak-to-peak No-load current μA  11  24  9  18 20 measured from peak-to-peak ¹Ultrasil 7000GR, Surface area - 175 m²/g ²Conductive Carbon Black (CCB), Printex XE2, Particle size, <30 nm, surface area 950 m²/g

Table 2 shows that optimal performances can be achieved with filler contents from 5 to 40 phr. This shows that proportions from 0.1% by weight to 50% by weight, as a proportion of the total mass of the second intermediate layer (i.e. the fourth layer) of an apparatus according to the invention, performs well. Particularly high performances were achieved in the range from 1% by weight to 10% by weight (cf. experiments E0 without filler, E1 with 10-phr silica and E3 with 5-phr carbon black).

Surface Roughness R_(a):

TABLE 3 Experimental data for the apparatus according to the invention with varying surface roughnesses Exp. Exp. Exp. Exp. Exp. Property Units V0 E1 E5 E3 E6 Materials used in the layers of an apparatus according to the invention 1st layer Copper Copper Copper Copper Copper 2nd layer PDMS PDMS PDMS PDMS PDMS 3rd layer Air Air Air Air Air 4th layer GECO GECO GECO GECO GECO 5th layer Copper Copper Copper Copper Copper Filler type in — Silica¹ Silica¹ Carbon Carbon the 4th layer black² black² (GECO) Thickness/ μm 120 120 120 120 120 transverse extent of the 2nd and 4th layer Filler weight phr 0 10 10 5 5 in the 4th layer as a percentage of the total weight of GECO Surface μm 0.3 0.3 3 0.3 3 roughness R_(a) of the 4th layer Results No-load V 125 185 181 153 237 voltage measured from peak-to-peak No-load μA 11 24 35 18 38 current measured from peak-to-peak ¹Ultrasil 7000GR, Surface area - 175 m²/g ²Conductive Carbon Black (CCB), Printex XE2, Particle size, <30 nm, surface area 950 m²/g

Table 3 shows that optimal performances can be achieved with surface roughnesses R_(a) in the range from 0.1 to 5 μm. This also applies to the surface roughnesses R_(a) of the second layer and to the range from 5 μm to 100 μm, in particular as shown in Table 3 for the range from 0.3 to 3 μm.

Layer Thicknesses of the Fourth Layer

TABLE 4 Experimental data of the apparatus according to the invention with varying thickness of the second layer Exp. Exp. Exp. Property Units V0 E7 E8 Materials used in the layers of the apparatus 1st layer Copper Copper Copper 2nd layer PDMS PDMS PDMS 3rd layer Air Air Air 4th layer GECO GECO GECO 5th layer Copper Copper Copper Filler type in the 4th layer — — — Thickness/transverse μm 120 60 250 extent of the 2nd layer Thickness/transverse μm 120 120 120 extent of the 4th layer Results No-load voltage measured V 125 61 63 from peak-to-peak No-load current measured μA 11 5 5 from peak-to-peak

Table 4 shows that optimal performance can be achieved with layer thicknesses in the range from 60 to 250 μm, especially with a layer thickness of 120 μm. This also applies to the layer thickness of the fourth layer. The layer thickness corresponds to the transverse extent of a layer of an apparatus according to the invention.

LIST OF REFERENCE SIGNS

-   1 first layer -   2 second layer -   3 third layer -   4 fourth layer -   5 fifth layer -   6 apparatus -   7 stabilization shell -   8 contacts between the electrode materials and the means of     measuring the voltage -   9 insulation material; compressible compound -   10 lack of negative charges -   11 additional negative charges; transmitted electrons -   12 mechanical force -   13 means of measuring the voltage between the first and fifth layers     of the apparatus; voltmeter -   14 axis of rotation; axial direction -   15 circumferential direction -   16 radial direction -   17 longitudinal extent -   18 transverse extent -   19 central axis of the apparatus -   20 longitudinal faces of the fourth layer -   21 longitudinal faces of the fifth layer -   22 longitudinal faces of the third layer -   23 geometric center of the third layer -   24 tire -   25 tread -   26 belt -   27 carcass -   28 inner liner -   29 measuring device for determining the performance of an apparatus     according to the invention -   30 flywheel for upward and downward movement of the first layer     (i.e. copper electrode) and second layer (i.e. first intermediate     layer) of the apparatus according to the invention -   31 piston for connecting the flywheel to the upper part of the     measuring device -   32 top part of the measuring device comprising the first and second     layer of the apparatus according to the invention -   33 bottom part of the measuring device comprising the fourth and     fifth layer of the apparatus according to the invention -   34 polycarbonate stamp -   35 polycarbonate base for fastening the fourth and fifth layer of     the apparatus according to the invention -   36 distance between the surfaces of the first and second layer -   37 diameter of the flywheel -   38 polycarbonate border with holes for escape and filling the     interior of the border with air -   39 oscilloscope 

The invention claimed is:
 1. A tire comprising: a tire tread and; an apparatus mounted in the tire tread for measuring mechanical forces of the tire during travel without additional electrical power, the apparatus comprising: a first layer, a second layer, a third layer, a fourth layer and a fifth layer, wherein: a) the first layer comprises a first electrode material; b) the second layer comprises a first intermediate material; d) the fourth layer comprises a second intermediate material and the third layer is between the second layer and the fourth layer and comprises an insulative material; and, e) the fifth layer comprises a second electrode material; the second or the fourth layer has a layer thickness in the range from 10 to 1000 μm; the first intermediate material of the second layer and the second intermediate material of the fourth layer are different, the layers and are arranged in order one on the other of the first layer, the second layer, the optional third layer, the fourth layer and the fifth layer, and wherein at least one of the second and the fourth layer further comprises at least one filler; the fourth layer is above the fifth layer, the second layer is above the fourth layer and the first layer is above the second layer; the first intermediate material is a terpolymer of epichlorohydrin, ethylene oxide and allyl-glycidyl ether; the second intermediate material is polydimethylsiloxane; the first and fifth layers configured to generate a voltage between them based on a mechanical force applied to the tire; a voltmeter for measuring the voltage; and a power storage charged by the voltage; a transmitter to generate a radio frequency (RF) signal from the voltage; and a control unit to evaluate the signal and determine a height of the voltage from the RF signal, the control unit mounted external from the apparatus and the tire.
 2. The tire according to claim 1, further comprising an accumulator attached to a wheel and charged by the voltage.
 3. The tire according to claim 1, wherein the second and the fourth layer have a layer thickness in the range from 10 μm to 1000 μm.
 4. The tire according to claim 1, wherein the second and the fourth layer comprises at least one additional filler material.
 5. The tire according to claim 4, wherein the at least one additional filler is a carbon black and a silica, wherein the silica of the second layer, is incorporated in an amount in the range of 0.1% to 50% by weight as a proportion of the total mass of the first layer.
 6. The tire according to claim 4, wherein the at least one additional filler is incorporated in an amount in the range from 0.1% by weight to 50% by weight based on the total mass of the first and/or fifth layer of the apparatus.
 7. The tire according to claim 1, wherein the first intermediate material of the second layer has a dielectric conductivity ε_(r) of greater than 10 F·m⁻¹ and the second intermediate material of the fourth layer has a dielectric conductivity ε_(r) of greater than 10 F·m⁻¹.
 8. The tire according to claim 7, wherein a difference between specific triboelectric affinity of the first intermediate material of the second layer and specific triboelectric affinity of the second intermediate material of the fourth layer is at least 20 nC/J, measured at 20° C. and at 35% relative humidity.
 9. The tire according to claim 1, wherein the third layer has a specific electrical conductivity of less than 10⁻¹ S·cm⁻¹ at 20° C.
 10. The tire according to claim 1, wherein the third layer comprises a support border formed of a vulcanized rubber or a thermosetting plastic, wherein a mixture is present in the support border, the mixture comprising one or more gases and/or particles of an insulating material, wherein the support border has a thickness of up to 200 μm and an electrical conductivity of up to 10 μS/m, or—as an insulating material, a liquid with a viscosity at 20° C. in the range from 0.1 mPa·s to 10⁶ mPa·s as measured using a rotary viscometer in accordance with DIN EN ISO
 3219. 11. The tire according to claim 1, wherein a central axis of the apparatus extends in a radial direction and runs in a direction of rotation of the tire.
 12. The tire according to claim 1, wherein the apparatus generates an electrical voltage and measures a mechanical force along the direction of rotation or the axial direction of the tire.
 13. The tire according to claim 1, the apparatus comprising a first state where the second and fourth layers are separated, a second state where the second and fourth layers are in contact, a third state to keep electrons transferred in the second state separate and generate the voltage.
 14. The tire according to claim 1, wherein a central axis of the apparatus extends in an axial direction. 